KITP
catdynamics | April 9, 2009"...we really do not understand the quantum theory in an intuitive manner because quantum laws are so radically different from the classical laws of physics. The dichotomy that the modern world is quantum, but the precise meaning of the quantum remains elusive, disturbed the stalwarts of physics such as Einstein, Schrodinger, and Feynman, and continues to baffle physicists even today. This lecture will explore this curious state of affairs..."
A few weeks ago, Prof Sankar Das Sarma gave a public lecture at the Kavli Institute on "Quantum Reality"
The online lecture is here - video and…
catdynamics | April 8, 2009final stretch and we contemplate big stellar clusters in small galaxies
in particular, if you plot the observed number of globular clusters as a function of galaxy magnitude you find the specific incidence, the number of globulars per unit light, is high for large ellipticals and small for Milky Way like spirals, but there is some evidence the specific incidence if also high for low luminosity dwarf galaxies
or is it...?
Fornax dSph from NS at Uppsala
Paul "finally I know how to pronounce his last name" Goudfrooji tutors us on globular clusters in late type dwarf galaxiesADS link
Is the…
catdynamics | April 7, 2009last week of the globs workshop, so the pace is stepped up, with two talks this afternoon
Michele on dynamical evolution (video and podcast)
32k runs, parametric over initial conditions
evolved mass function, primordial binaries, tidal field, variable initial concentration, IMBH presence
Glenn on dynamical Schwarzschild modeling (video and podcast)
Schwarzschild orbit models
First intro to state of the art for fitting galaxy models
using Sauron integral field spectroscopy plus photometry
and get h3 and h4 of course (gaussian weighted skew and kurtosis for you heathens)
Nice models
then…
catdynamics | April 7, 2009back from a brief but complex zig zag across the Southland
and we are getting ready to wrap up the globs workshop
if only we could find someone to organise the final thursday dinner...
what all happened:
yesterday Tom did a recap of the 5th UC Irvine Center for Cosmology workshop: Intermediate-Mass Black Holes: from First Light to Galactic Nuclei which had a large number of very exciting and topical talks by top researchers.
Top researchers I tell you.
Before that there were talks on open clusters:
Jarrod - video and podcast andAaron - video and podcast
Today Douglas tutors us on N-body…
catdynamics | April 2, 2009Bob!
We move on to open clusters, in the hope that we may actually understand those, since they are smaller and more tractable for simulations, right?
Right...
Open Clusters
"All you have to do is just go look..."
NGC 3293
Typical densities - few per cubic parsec
velocity dispersion ~ km/sec
core radius ~ 1 pc
tidal radius ~ 10-20 pc
half mass relaxation time ~ 100 Myrs - ages from zero to several Gyrs
metallicities - -0.4
But what about NGC 6791 - old massive and metal rich... globular or open?
click to embiggenNGC 6791
ok, so what we really need is a sensible definition of what is an…
catdynamics | March 31, 2009This beautiful tuesday morning, Dave tutors us on relaxation and cluster core collapse.
Then it is party at Alison's place.
But, first, we go through thermodynamics of self-gravitating internally relaxed systems, multiple equilibria and general dimensionless solutions.
Open Cluster M7 (from Utahskies.org)
Globular cluster M4 (from Utahskies.org)
Core collapsed? Or not?
Globular cluster M15 (from Utahskies.org - ok actually hubblesite, but they had a scaled copy and I was on a roll)
Definitely core collapse, we think.
Seriously - there are more core collapsed or post-core collapsed…
catdynamics | March 31, 2009Steven Simon from Oxford University gives the Director's Blackboard Talk:"Interesting and Useful" (video and podcast)
catdynamics | March 30, 2009Questa confusione non mi piace!
Parli piu silenziosamente, per favore.
Seriamente, ho mal di testa.
Si, si, pero avete considerato i campi magnetici?
Fermate, per favore.
Personalmenta, credo che il cafe espresso e disgustoso!
The Clusters09 Guide to Defusing Italian Discussions in the Morning Session (pdf)
For some strange reasons, the above list of romanic pseudo-code appeared on a KITP blackboard a couple of weeks ago.I think it appeared when we were discussing Y and multiple populations...
Fortuitously, the list was preserved for posterity, so that future generations may have productive…
catdynamics | March 30, 2009The dynamics workshop in back, refreshed and ready to rock with yet more people in place.
This morning Melvyn tutors us on planets.
In globular clusters.
Planets in globulars clusters?!
From the CfA wallpaper collection - very nice images btw
Well, yes, maybe.
Or, more generally planets in very dense stellar associations.
Dynamically planets tend to get stripped quickly if they are orbiting at more than a few AU in a typical cluster.
But, planets closer in can stick around for gigayears, and those tend to be the ones we can observe.
We looked...
we found something interesting elsewhere...…
catdynamics | March 26, 2009intense and dense afternoon as we get the current state of the art about neutron star natal kicks, theory and observational constraints
Chevy supernova!
Vicky - on NS-NS constraints (video and podcast)
need >~ 2.1-2.3 solar mass He cores to get to iron and classic type II SNe
stable mass transfer may lower this limit
electron capture supernovae, in binaries, may limit on core masses right before SNe town to ~ 1.45 solar masses or more
evidence other than presence in globulars for subpopulation of neutron stars having low kick speeds: high mass x-ray binaries with e 30 days
- unlikely…
catdynamics | March 26, 2009Phil tutors us today on neutron star formation and retention in globulars.
So we expect neutron stars to be made in globular clusters.
Massive metal poor stars should undergo supernovae and make neutron stars for a mass range of ~ 8-15-or-20 solar masses, maybe more or less, and depending a little bit on whether they are in a tight binary.
More massive stars may, or may not, make stellar mass black holes. But we are not here to talk about black holes, at least not this part of this morning.
So, when type II supernovae go bang (and we're not totally sure yet of the details of how that works,…
catdynamics | March 25, 2009Tom leads today, talking some more about Intermediate Mass Black Holes and possible evidence for black holes in globulars.
NGC 4472 in x-rays
ok, so there is probably a black hole in a globular in NGC 4472, and this, and the discovery paper
and very nice it is too
variable point x-ray source (well, XMM detection...) in a globular
at about 20 times Eddington luminousity, for a neutron star, in a high state
seen a transition to factor 7 lower state, mostly due to deficit of sub keV component, indicative of local foreground absorption
interesting... someone give them some XMM and/or Chandra…
catdynamics | March 24, 2009you'd think that clusters that are bigger ought to be more massive, and vica versa.
ah, but are they? Arunav discusses
cf figure 2 in Kissler-Patig et al 2006
which was by all accounts a most invigorating and energetic discussion
but I missed 95% of it, as my paymasters required my presence in another realm
for the afternoon's entertainment
Andreas (video and podcast) discusses modeling of tidal tails, specifically Pal 5
Pal 5
and
Mario (video and podcast) discusses the ongoing hunt for evidence for IMBHs in galactic globulars
NGC 2298
yup, that NGC 2298
catdynamics | March 23, 2009Astrophysicists like to quantify their estimates. One way to do that is to offer bets, with odds, on hypotheses or models being correct. There have been some famous bets, with spectacular odds.
We now have a new one, and a very daring one too.
Prof. Cole Miller gave today's Director's Blackboard talk:
Black Holes in Dense Star Clusters (video and podcast)
The main focus of the talk are the much speculated about "Intermediate Mass Black Holes" - black holes too massive to have descended from single stars, but not really the "Supermassive Black Holes" found in the centers of (most) galaxies.…
catdynamics | March 23, 2009the sun is back, and so is the intrepid gang of globularists here at the Kavli institute
apparently this week is gravitational radiation sources, with primary focus on intermediate mass black holes - including evidence hinting at their possible presence, and the possible fun things we can do with them
blackboard lunch today is on IMBHs, and will be webcast in due course as will an unusually high proportion of this weeks talks
PS: Cole left up a handy dandy gravitational radiation tutorial (pdf)
catdynamics | March 19, 2009
Bit behind with KITP program events, mostly due to my deplorable inability to be in two or more places at the same time.
Bit on multiple populations, and then gravitational radiation sources.
Franca d'Antona's talk on multiple stellar populations is here - thought we knew simple main sequence stars?
Hah!
Worried?
You ought to be...
I'll be getting back to multiple populations and why some of us are worried later.
Richard on gravitational waves here follow by Ilya here
Another topic due to get heated.
More on that next week.
catdynamics | March 17, 2009stars do turn, sometimes fast enough to be noticeably flattened
this may have consequences
Like So
there are two issues related to stellar rotation contemplated this morning:
Altair
now, way flatter than that...
self-enrichment - back to the good old O/Na anti-correlation
evidence for H burning at high T
trick is not so much to burn the H, but to get the ashes out...
can do that either with AGB stars, yes, it is the dreaded "third dredge up", or just boring old hot bottom burning... ok, don't ever google that.
AGB dredge up (from Eskridge's online lecture notes at MNSU)
anyway, to get…
catdynamics | March 17, 2009I now know who to blame for this science blogging thing
I was a little bit bemused when I arrived at KITP and was told, by the way, that the program needed an official blogger, and that I, for my sins and in recompense, was it.
It is all Jennifer's fault,
she thinks it is all parties and cocktails over there at twisted physics, but then someone else ends up doing the work... though I must say the wine the other night was rather excellent...
anyway, go read her rationale and general guide to physics blogging, combined with podcast and video - you might even start your own blog
actually, the…
catdynamics | March 16, 2009lovely day, here at the beach
we have a busy week, the start of a busy month
we'll be doing multiple populations in depth, again,
and yet more on IMBH
this morning we contemplate, via Mario, whether globulars occupy a fundamental plane like galaxies, maybe even the same plane
log(Re) = 1.24 log(σ) + 0.33 SBe - 8.895 (for galaxies)
refs Djorgovski 1995 and Pasquato & Bertin 2008
1.24? 1.24!
Observers are soooooooo silly sometimes.
Clearly it must be 5/4 and 1/3
I mean 31/25 is just a silly number.
There is still a fundamental plane though P&B have somewhat different slope and a zero…
catdynamics | March 13, 2009Fermi Gamma-ray Telescope has results.
We hear about them.
why, yes, that really was 47 Tuc
"Discovery of γ-ray sources from the globular cluster 47 Tuc" or something similar, in preparation, at a glossy journal near you soon
in the mean time, browse the LAT bright source catalog (for high galactic latitude - none has dared descend into the plane yet...)
this will really screw up starry eyed particle (astro)physicists who were desperately hoping to find cold dark matter annihilation radiation from substructure in the halo
hah!
we temporarily ignore gamma-ray bursts...
we will return to your…